1. Technical Field
The present invention relates to an optical disk drive, and more particularly to transfer control of an optical pickup.
2. Related Art
An optical disk drive has hitherto performed seeking operation by means of transferring an optical pickup in a radial direction of an optical disk by means of a stepping motor.
FIGS. 5 and 6 show the configuration of an optical disk drive and the configuration of a transfer mechanism, which are described in the related art shown in JP2003-100041A. An optical pickup 310 has a semiconductor laser (LD) and emits a laser beam modulated according to recording data, thereby recording data on an optical disk 10; and emits a laser beam of reproducing power and receives light reflected from the optical disk 10, to thus generate a reproduced signal.
A decoder 320 decodes the reproduced signal from the optical pickup 310; generates an address signal or the like; and supplies a control section 330 with the thus-generated address signal or the like.
The control section 330 comprises a CPU, ROM, RAM, and the like, and controls seeking operation. Specifically, upon receipt, from a host machine such as a personal computer or the like, of a seeking operation command including a target address corresponding to a destination where the optical pickup 310 is to be transferred, the control section 330 computes the number of pulse signals to be imparted to a stepping motor 100, and supplies a controller 340 with the number of pulse signals. In accordance with the command from the control section 330, the controller 340 supplies a driver 350 with a drive control signal. In accordance with the drive control signal, the driver 350 controls the number of rotations of and the rotational speed of the stepping motor 100.
As shown in FIG. 6, the stepping motor 100 is provided with a lead screw 110 in which a helical groove is formed at a given pitch P, and the lead screw 110 is mounted in parallel with the radial direction of the optical disk 10. The optical pickup 310 is disposed so as to be movable along the groove of the lead screw 110. Every time the stepping motor 100 rotates one turn, the optical pickup 310 is moved in the radial direction of the optical disk 10 at one pitch P of the lead screw 110.
With such a configuration, the control section 330 computes a difference between the current address supplied from the decoder 320 at the end of seeking operation and the target address received from the host machine at the commencement of seeking operation. When the computed amount of displacement exceeds an allowable amount, the stepping motor 100 is determined to be out of step (hereinafter called “step-out”), and the rotational speed of the stepping motor 100 is reduced. Here, the term “step-out” means a phenomenon in which the torque of the stepping motor 100 becomes deficient for reasons of an increase in a pulse frequency applied to the stepping motor 100 and which the stepping motor 100 does not rotate even when the pulse voltage is applied to the stepping motor 100.
Meanwhile, it is desired to be able to prevent dissociation of the current address from the target address by reliable detection of the step-out during seeking operation rather than by detection of the step-out at the end of seeking operation.
Even when the step-out is detected at the end of seeking operation, detection of step-out with higher accuracy is desired.
Further, when the optical pickup 310 is transferred, in addition to step-out, tooth jump; namely, disengagement of a teeth section 310a provided in the optical pickup 310 from the lead screw, may arise. Reliable detection of such tooth jump is desired.